In endoscopy it is frequently necessary to heat tissues selectively for local application of heat or for coagulation, wherein basically a distinction is to be made between methods in which heat transfer takes place with direct contact of the tissue and methods in which heat transfer to the tissue takes place indirectly.
For instance, in DE-A-3 642 077 there is disclosed a device for high-frequency cutting and/or coagulation or for laser application. A further electrosurgical coagulation device is known from DE-A-3 710 489. Finally, from open surgery are also known cauterising tools for coagulation by means of gases, for example from EP-A-0 447 121 or from DE-C-75 016.
In the endoscopic use of such heat applying or coagulating instruments, the instrument for regional treatment of the body cavity with heat is for example introduced into the body cavity by a trocar. In such interventions the body cavity is frequently expanded, for which purpose gases are used, the gases being conducted under excess pressure into the body cavity. In coagulation by means of the above-mentioned devices, gases are produced which must be extracted from the body cavity, as they impair the view of the surgeon. In order to maintain the expansion of the body cavity, frequent postinsufflation of the supporting gas is therefore necessary.
In endoscopic use, the adaptation of gas coagulators of the kind described above does not offer a solution avoiding the disadvantages stated, because such devices in particular also have the disadvantage that in the case of incomplete combustion of the combustible gases used an explosive mixture can be formed. In the case of the subject according to DE-C-75 016 this mixture could be caused to explode by the open flame, or in a device according to EP-A-0 447 121 an explosion could be brought about due to arcing by the electrodes. Moreover with these methods residues would be formed by combustion of the gases, which would have to be removed very carefully from the body cavity.
The above-mentioned disadvantages concern first and foremost requirements connected with the necessary extraction of smoke and maintenance of the body cavity expansion. The disadvantages of electrically operated coagulating devices lie in particular in that basically an electrical potential is applied to the patient, owing to which in case of any breakdowns of the electrical system, for example due to insulation faults, there can be considerable danger to the patient. Potential-free systems such as laser coagulators are by contrast very elaborate and difficult to handle.